Self-injurious behavior (SIB), e.g., wrist cutting, burning, may serve a mood regulatory function in patients with borderline personality disorder (BPD). Recent attention has focused on possible biological contributions to the mediation of SIB in these patients. Moreover, there is clinical evidence that pain perception and mood regulation may be abnormal in these individuals. If, so studying pain perception and mood regulation may provide a rational inroad to investigating biological underpinnings of SIB. We recently found that pain ratings during the cold pressor test (CPI) were significantly decreased in self-injurious BPD patients who report that they do not feel any pain during self-injury (BPD-NP), compared to those who report that they feel pain (BPD-P), and normal controls. Mood improved in the BPD-NP group, but not in the latter groups, following the CPT (Russ et al, 1992). Taken together, these data support the usefulness of the CPT as a laboratory procedure to test particular hypotheses about SIB, as well as the possibility that pain perception and mood regulation are abnormal in some self-injurious patients, i.e., the BPD-NP group. These results, however, do not demonstrate neurophysiological differences among groups with respect to pain perception. The experience and report of pain are subject to a variety of affective, cognitive and personality influences. The overall aim of the proposed study is to investigate neurosensory differences related to pain among these groups (and a group of patients with major depression). We will use two types of painful stimuli (cold, heat) employed in two pain perception protocols (Signal Detection Theory paradigm, BEG Cortical Power Spectrum Density analysis) in order to explore differences in neurophysiological correlates of subjective pain. We will also assess possible psychological and historical contributions to observed differences in pain report.